The present invention relates to an electric steering column apparatus which holds a steering shaft to be rotatable and can electrically adjust the position of a steering wheel.
A conventional electric steering column apparatus is disclosed, for example, in Japanese Patent No. 2647476. In this apparatus, since a steering wheel is arranged at desired axial position and vertical position, the arrangement is such that a tilt joint or a telescopic joint is provided and a tilt position or a telescopic position of the steering wheel can be adjusted by means of an actuator which comprises an electric motor and a screw mechanism. Then, there is also provided a switch mechanism by which the electric motor is operated only when a working force of a predetermined level or higher is applied in a predetermined direction of the steering wheel, so as to electrically adjust the tilt position or the telescopic position (axial position) of the steering wheel.
However, in the above-mentioned electric steering column apparatus, the tilt position or the telescopic position of the steering wheel can not be detected. It is important to detect the position of the steering wheel, in order to finely adjust or control the position of the steering wheel. When the position of the steering wheel is to be detected, a brush or a rotary encoder or a linear encoder using a variable resistance, or the like, is usually employed. However, with such means, accurate detection may not be obtained due to abrasion of contacts, etc., for a long term use.
Also in the above-mentioned electric steering column apparatus, a tilt actuator (that is, an actuator for adjusting the tilt position of the steering wheel) and a telescopic actuator (that is, an actuator for adjusting the telescopic position of the steering wheel) are different components separately provided, so that the number of the constituent parts for steering must be increased, which causes a decline of mass productivity, etc., of the actuator and necessity for selecting two kinds of actuators in assembling the steering apparatus, and, in consequence, hinders the reduction in the manufacturing cost and the assembling steps.
For example, the electric tilt steering apparatus is generally arranged such that a rod is extended or contracted through a worm gear by an electric motor provided on a lower steering column, and an upper steering column coupled to an end of this rod through a bracket is moved in an inclined manner, whereby an angle of inclination of the steering wheel is adjusted to a desired angle.
In an electric tilt steering apparatus of a so-called upper part rocking type disclosed, for example, in Japanese Utility Model Publication No. 5-29979, an upper steering shaft is rockably coupled to a lower steering shaft through a universal joint and an upper steering column is rockably coupled to a lower steering column through a pin, correspondingly thereto. An electric motor for extending or contracting a rod through a worm gear is mounted on the lower steering column, and an end of this rod is coupled to a bracket which is provided on the upper steering column. With such arrangement, the rod is extended or contracted by the electric motor to incline the upper steering column with respect to the lower steering column fixed to the car body, thereby adjusting an angle of inclination of the steering wheel.
On the other hand, in an electric tilt steering apparatus of a so-called lower part rocking type disclosed in PCT Japanese Phase Publication No. 7-506308, a steering column is arranged to be integrally inclined with the position of a universal joint provided in a lower part of a steering shaft, as a center of a tilt movement, while the steering column is arranged to be movable a little in the axial direction with no tilt center, such as a pin. Further, a bell crank which is rocked by an electric motor is coupled to this steering column, whereby the bell crank is rocked by driving the electric motor so as to incline the steering column. When this bell crank is rocked, an axial force is generated to move the steering column in the axial direction. However, since the steering column is arranged to be freely movable in the axial direction, this axial force can be absorbed.
However, in the electric tilt steering apparatus of the so-called upper part rocking type disclosed in the above-mentioned Japanese Utility Model Publication No. 5-29979, both the steering shaft and the steering column are divided into upper and lower parts, respectively, which is disadvantageous in terms of the manufacturing cost because of the increased number of the constituent parts.
Also, since the rod of the electric motor is arranged to support the upper steering column and the upper steering shaft, if a load (vibration) is input downward and toward a front part of the car from the steering wheel side, this load (vibration) in the vertical direction directly works upon the rod and the rod receives most of this load (vibration). For this reason, the rigidity of this rod is required to be very high, and measures for suppressing backlash which may caused by the vibration of the rod are required to be fully taken.
Further, in the electric tilt steering apparatus of the so-called lower part rocking type disclosed in PCT Japanese phase Publication No. 7-506308, since the steering column has no tilt center such as a pin, if a load (vibration) is input downward and toward a front part of the car from the steering wheel side, this load (vibration) in the vertical direction directly works upon the telescopic portion of the steering shaft and this telescopic portion receives most of this load (vibration). For this reason, in order to secure a smooth operation of this telescopic portion or to prevent backlash due to the vibration of the telescopic portion, full measures are required to be taken for the telescopic portion.
The present invention was contrived taking the above circumstances into consideration, and an object of first and second aspects of the invention is to provide an electric steering column apparatus which can detect the tilt position or the telescopic position of the steering wheel easily and accurately and can realize reduction in the manufacturing cost by rendering the constituent parts for common use.
According to the first aspect of the present invention, there is provided an electric steering column apparatus which comprises a steering shaft having a steering wheel mounted on a rear end thereof, a steering column for rotatably supporting this steering shaft, an electric actuator for adjusting the position of the steering shaft by driving this steering column, and position detecting means for detecting the position of the steering shaft in a non-contact manner.
In this electric steering column apparatus, since the position detecting device detects the position of the steering shaft in a non-contact manner, it becomes possible to detect the position of the steering wheel easily and accurately, whereby it also becomes possible to finely adjust or accurately control the position of the steering shaft. Note that if the position of the steering shaft is detected by a sensor of a contact type, such as a direct-acting resistance sensor, such sensor is inferior to that of the non-contact type in terms of the durability, and an accuracy in the position detection is declined since a range of a difference in voltage is not fully secured. Further, such non-contact type sensor is less influenced by noises and a fluctuation in temperature, compared with that of a contact type.
Note that the position of the steering wheel denotes the tilt position which is corresponding to an inclination of the steering wheel, or the telescopic position (axial position) corresponding to an amount of the movement of the steering wheel due to the telescopic movement of the steering shaft.
The position detecting device preferably effects detection digitally. The position detecting device may be constituted by, for example, a magnetic pulser device for generating a signal corresponding to a rotation of the electric motor, an optical pulser device, a dielectric pulser device, an electric capacity pulser device, etc. With such arrangement, it becomes possible to conduct reliable position detection with high durability and high reproducibility.
A pulser device for forming the position detecting device may be arranged integrally with the electric motor. With this arrangement, it becomes possible to conduct position detection based on an amount of rotation of the electric motor, so that the position detecting device can be made compact and precise, and the position detection of the steering wheel can be conducted simply with precision.
Also, if the electric motor is a DC brush motor, it is possible to effect the position control by using a ripple voltage or a high level noise as a pulse. Further, if the electric motor is a DC brushless motor provided with a rotation position detecting mechanism comprising a Hall element, a tacho-generator, and the like, it becomes possible to detect the position of the steering wheel on the basis of an output from such rotation position detecting mechanism.
When the position detecting device is integrally formed with the electric motor, an appropriate extension/contraction mechanism is further provided for shifting the steering column by converting a rotation of the electric motor into a linear movement and this extension/contraction mechanism, the electric motor, and the position detecting device can be formed in a unitary structure. When the tilt position and the telescopic position of the steering wheel are adjusted independently of each other, the extension/contraction mechanism, the electric motor, and the position detecting device formed in a unitary structure as mentioned above can be provided for each of the tilt position and the telescopic position. In this manner, it is possible to reduce the number of steps for the adjustment and the number of kinds of the constituent parts, to thereby save the manufacturing cost.
According to the second aspect of the present invention, there is proposed an electric steering column apparatus which comprises a steering shaft having a steering wheel at the read end thereof, a steering column for rotatably supporting this steering shaft, and capable of a tilt movement around a tilt pivot and a telescopic movement along the axial direction of the steering shaft, an electric tilt actuator used for the tilt movement of the steering column, in which the electric tilt actuator and the electric telescopic actuator have one and the same structure and are composed of the same parts, respectively.
According to this invention, since the electric tilt actuator and the electric telescopic actuator have one and the same structure and are composed of the same parts respectively, it is possible to cut down a metal mold for producing the main body of the actuator and to enhance the mass productivity thereof. Additional, it is possible to realize facilitation of the assembling works and rationalization of the assembling steps.
In an electric steering column apparatus according to the first or second aspect of the present invention, the electric actuator comprises an electric motor which is supported by the main body of the actuator and a rod driving mechanism, and the rod driving mechanism can be provided with a gear shaft which comprises a driven gear portion to be driven by a driving gear on the electric motor side and a shaft portion rotatably held on the main body of the actuator through a bearing. According to this invention, it is possible to easily realize enhancement of the mass productivity of the apparatus and reduction in weight, by forming the gear shaft in a unitary structure of synthetic resin.
Also, in the above-mentioned electric steering column apparatus of the present invention, it is possible to form a first deformation portion projecting from the inner diameter of the bearing on the outer peripheral surface of the shaft portion. According to this feature of the present invention, it is possible to maintain a constant pressing force for thrusting the shaft into the inner race of the bearing, by forming ridges or annular protrusions, or the like, as the first deformation portion, for example, on the outer peripheral surface of the shaft portion, and plastically or elastically deform the first deformation portion. Thus, an amount of deformation (an amount of contraction of the size) of the shaft portion can be prevented from being unnecessarily large.
Also, according to this feature of the present invention, in the above-mentioned electric steering column apparatus, a second deformation portion which is in contact with a side of the inner race of the bearing can be formed on a side of the driven gear. According to this feature, it is possible to control preload of the bearing in assembling easily and with certainty, by forming radial ridges or concentric protrusions, or the like, as a second deformation portion, for example, on a side of the driven gear, and plastically or elastically deforming the second deformation portion.
Also, according to the present invention, in the above-mentioned electric steering column apparatus, there may be provided an actuator rod with a female screw formed on the axis of the gear shaft and a male screw to engage the actuator with the female screw, and a groove for retaining lubricating oil may be formed on the female screw. According to this feature of the present invention, if, for example, metric thread screws which can be easily processed are employed as the female screw and the male screw, the engaged portion can be lubricated with grease, or the like, supplied from the lubricating oil retaining groove. Thus, it is possible to obtain a smooth operation and long-term durability of the apparatus.
Also according to the present invention, in the above-mentioned electric steering column apparatus, the driven gear portion can be constituted by a gear base, a ring gear fitted on this gear base, and an elastic member interposed between the gear base and the ring gear. According to this feature of the invention, it is possible to reduce backlash sound or the like at the time of reversal rotation of the electric motor, as well as abrasion of the driving gear and the ring gear.
According to a third aspect of the present invention, it is aimed to provide an automatic tilt or telescopic type steering apparatus on which a bracket on the inner barrel side to be coupled to a rod of a drive portion for a tilt or telescopic operation can be fixedly mounted with accuracy by a simple method. In order to achieve this object, there is provided, according to the third aspect of the present invention, an automatic tilt telescopic type steering apparatus in which an inner column member of a steering column is slidably fitted in an outer column member to extend or contract a rod of a drive portion to thereby move the inner column member in the back and forth direction of the car with respect to the outer column member, whereby the axial length of the steering column and an angle of inclination of the column are automatically adjusted. Such steering apparatus is characterized in that a bracket on the inner column member side to be coupled to the rod of the drive portion comprises an auxiliary member attached to the inner side of the inner column member in advance, and the main body of the bracket to be assembled in this auxiliary member through an opening of this inner column member.
As described above, according to the third aspect of the present invention, it will be suffice if the bracket on the inner column member side to be coupled to the rod of the drive portion is formed by assembling the main body of the bracket in the auxiliary member through the opening of the inner column member, after attaching the auxiliary member to the inner side of the inner column member in advance. Accordingly, the bracket can be attached very easily, and moreover, the bracket can be attached fixedly with accuracy without welding or other processing. Further, sliding movement of the inner column member with respect to the outer column member can be conducted smoothly. In addition, the manufacturing cost is not increased and the size of the apparatus can be reduced.
According to a fourth aspect of the present invention, it is aimed to provide an automatic tilt steering apparatus which does not incur rise in the manufacturing cost and does not require a high rigidity for the rod and high-level measures for preventing backlash.
In order to achieve this object, according to the fourth aspect of the present invention, there is provided an automatic tilt steering apparatus for adjusting an angle of inclination of a steering wheel by automatically inclining a steering column, characterized in that:
a tilt center is provided at the lower end of the steering column in a front part of the car so that the steering column is integrally moved in an inclined manner, while a universal joint is provided at the lower end in the front part of the car so that the steering shaft can be also moved in an inclined manner correspondingly to this tilt center;
a rod to be extended and/or contracted by a drive portion is engaged with a tilt rocking member which is rockably provided on the car body through a bracket, while a slide frame portion is provided on this tilt rocking member for causing a sliding piece projecting from the steering column to slide; and
in consequent, when the rod of the drive portion is extended and/or contracted and the tilt rocking member is caused to rock, the sliding piece is caused to rock, while sliding inside the slide frame portion, together with the steering column, so as to incline this steering column.
As described above, according to the fourth aspect of the present invention, there is arranged a so-called lower part rocking type steering apparatus in which the tilt center is provided at the lower end of the steering column in a front part of the car to move the steering column integrally in an inclined manner, while the universal joint is provided at the lower end in the front part of the car so that the steering shaft can be also inclined correspondingly to this tilt center.
Also, while the rod which is extended or contracted by the drive portion is engaged with the tilt rocking member which is rockably provided on the car body through the bracket, the slide frame portion for causing the sliding piece projecting from the steering column to slide is provided on this tilt rocking member. With this arrangement, at the time of tilt adjustment, the tilt rocking member is rocked by extending or contracting the rod of the drive portion, whereby this steering column is moved in an inclined manner while the sliding piece is caused to slide inside the slide frame portion to be rocked together with the tilt rocking member.
Accordingly, since this steering apparatus is not of the so-called upper part rocking type, there is no need to divide the steering shaft and the steering column into upper and lower parts, whereby the number of the constituent parts can be decreased to reduce the manufacturing cost.
Also, when a load (vibration) is input downward in a front part of the car from the steering wheel side, this load (vibration) in the vertical direction indirectly works upon the rod at a predetermined lever ratio through the tilt rocking member, so that the rigidity of the rod is not required to be very high and very high level measures are not required for preventing a backlash which may be caused by the vibration.
Further, in PCT Japanese Phase Publication No. 7-506308, the bell crank is rocked to move the steering column in an inclined manner at the time of tilt adjustment. However, in this case, the bell crank is not only rocked, but is moved in the axial direction, so that the movement of this bell crank in the axial direction is absorbed due to the structure in which the steering column is freely moved in the axial direction. However, with this structure, a tilt center such as a pin can not be provided on the steering column, and the steering column cannot receive a load or vibration in the axial direction from the steering wheel.
On the other hand, according to the fourth aspect of the present invention, it is arranged such that, at the time of tilt adjustment, the tilt rocking member is rocked and the sliding piece is rocked together with the steering column while sliding in the slide frame portion, so that the movement in the axial direction generated in the tilt rocking member is absorbed by causing the sliding piece to slide in the slide frame portion. For this reason, a tilt center such as a pin can be arranged at the lower end of the steering column and the steering column can receive a load or vibration in the axial direction from the steering wheel.